Lightweight closure and container package

ABSTRACT

A closure and container package for pressurized products, such as carbonated beverages, includes a closure comprising a closure cap having a top wall portion, and an annular skirt portion depending from the top wall portion. Features of the closure construction, and selection of the polymer from which the closure is formed, permits the closure to meet sealing, impact resistance, and other performance criteria, with desirably reduced use of polymeric material. Significant cost savings can thus be achieved.

TECHNICAL FIELD

The present invention relates generally to a closure and container package for carbonated beverages and the like, wherein the closure has been specifically configured for reduced use of polymeric material, while at the same time providing the required sealing performance for the carbonated contents of the package.

BACKGROUND OF THE INVENTION

Molded plastic closures formed from suitable polymeric materials have met with widespread acceptance in the marketplace. Closures of this nature, typically formed by compression molding or injection molding, have proven to be especially effective for use on containers having carbonated or otherwise pressurized contents. Experience has shown that providing effective sealing of a package having carbonated contents ordinarily requires a highly engineered closure to ensure effective sealing under a range of temperature and handling conditions. Additionally, closures of this nature typically include tamper-evident features, such as a tamper-indicating pilfer band, to assure consumers of product freshness quality.

As will be appreciated, a significant cost associated with closures of this nature is the polymeric material from which the closures are molded. Polypropylene, polyethylene, copolymers, and like polymeric materials are typically employed for manufacture of these types of closures. In view of the very large number of closures which are typically used for any particular product, any reduction in the amount of polymeric material for closure manufacture can desirably result in significant cost savings.

The present invention is directed to a closure and container package, including a light-weight closure which has been specifically configured for reduced use of polymeric material, while still providing the requisite closure performance, including sealing performance, while at the same time providing a tamper-evidence function for ensuring package integrity.

SUMMARY OF THE INVENTION

A closure and container package embodying the principles of the present invention has been specifically configured for packaging carbonated products, such as carbonated beverages, or other pressurized products. Notably, the closure of the package has been specifically configured to require relatively reduced quantities of polymeric material, while at the same time providing the necessary sealing performance, and desired tamper-indication function.

In accordance with the illustrated embodiment, a lightweight closure embodying the principles of the present invention can be configured as a unitary, one-piece closure molded from polymeric material. The closure comprises a closure cap having a top wall portion, and an annular skirt portion depending from the top wall portion. The skirt portion includes an external knurl pattern, and an internal thread formation for threaded engagement with an external thread formation of an associated container.

In order to provide the desired tamper-indication function, the present lightweight closure includes a tamper-evident band at least partially detachably connected to the skirt portion of the closure cap. The tamper-evident band is detachably connected to the skirt portion by a plurality of circumferentially spaced frangible bridges, each of which is defined between circumferentially spaced scores that extend into the closure between the skirt portion and the tamper-evident band.

Notably, the development of the present closure has found that use of certain polymeric formulations, having a certain density, can be most cost-effective, while providing the desired level of closure performance. To this end, the present closure if preferably formed from high-density polyethylene polymer having a density of about 0.945 g/cm to about 0.97 g/cm. In one current embodiment, high-density polyethylene having a density of 0.955 g/cm has been successfully employed.

An important aspect of meeting the required performance characteristics for a closure used on carbonated beverages and the like is the dimensional consistency of the closure, notwithstanding variations in the polymer formulation. To this end, the polymer formulation preferably include a nucleator when a colorant is provided in the polymer, to thereby minimize dimensional variations of the closure. The polymer also preferably includes approximately 0.2 to 0.3% lubricant, by weight.

As noted, the present closure can be configured as a unitary, one-piece constructions, and to this end, preferably includes integral sealing features for sealing cooperation with the associated container. In the illustrated embodiment, the closure includes a substantially continuous, annular sealing element depending from the top wall portion inwardly of the annular skirt portion of the closure cap. The outer seal element is generally annular, and defines a generally inwardly facing sealing surface for engagement with a generally outwardly facing sealing surface of the associated container.

The sealing performance of the outer seal element is enhanced by provision of a plurality of circumferentially spaced, seal reinforcement elements on the inside surface of the skirt portion radially outwardly of the outer seal element, adjacent the top wall portion of the closure cap. The reinforcement elements are engageable by the outer seal element to limit outward deflection of the outer seal element, to thereby enhance sealing cooperation of the outer seal element with the associated container, and improve the impact resistance of the closure.

In the preferred form, the present closure further includes an inner plug seal element depending from the top wall portion of the closure cap. The plug seal element is generally cylindrical, and defines an outwardly facing sealing surface for sealing engagement with a generally inwardly facing, inside surface of the associated container.

In the preferred form of the present closure, the internal thread formation of the closure cap is specifically configured to promote closure performance, while minimizing use of polymeric material. To this end, the internal thread formation is preferably configured to provide a variation in retention force which decreases in a direction away from the top wall portion of the closure cap. Generally speaking, this is achieved by providing a varying thread geometry for the internal thread formation, with the internal thread formation having a larger cross-section toward the top wall portion of the closure cap to provide more resistive force.

As noted, the present closure has been specifically configured to provide a tamper-indication function, with the tamper-evident band of the closure being detachably connected to the annular skirt portion of the closure cap. In accordance with the illustrated embodiment, the tamper-evident band includes an annular band portion depending from the skirt portion that is detachably connected thereto, and an annular inner flange portion extending inwardly from a lower margin of the annular band portion. Notably, the inner flange portion defines a plurality of circumferentially spaced openings, spaced from a free edge thereof. The closure pilfer band has been specifically configured to provide the desired tamper-indication performance, while minimizing the quantity of polymeric material from which the band is formed. In the preferred form, the tamper-evident band has a maximum outside dimension which is substantially aligned with a maximum outside dimension of the skirt portion at the external knurl portion thereof.

Notably, a closure embodying the principles of the present invention has been found to provide all necessary performance characteristics, with a current embodiment thereof weighing approximately 1.95 g, and having an Aggregate Lightweight Performance Index of at least about 40.

Other features and advantages of the present invention will become readily apparent from the following detailed description, the accompanying drawings and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded, side elevational view, partially cutaway, showing a closure and container package for carbonated products embodying the principles of the present invention;

FIG. 2 is a cross-sectional view of the closure shown in FIG. 1; and

FIG. 3 is a cross-sectional view similar to FIG. 2 showing the closure in its configuration after ejection from an associated mold, wherein a tamper-evident band of the closure is unscored, and in an orientation in which it is molded.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

While the present invention is susceptible of embodiment in various forms, there is shown in the drawings and will hereinafter be described a presently preferred embodiment, with the understanding that the present disclosure is to be considered as an exemplification of the invention, and is not intended to limit the invention to the specific embodiment illustrated.

With reference now to the drawings, therein is illustrated a closure and container package 10 for carbonated or otherwise pressurized contents, including a lightweight closure 12 embodying the principles of the present invention, and a container 14 having a threaded neck portion that includes an external, helical thread formation 16. The thread formation terminates at an annular locking ring 18, which cooperates with closure 12 for tamper-indication. As will be familiar to those skilled in the art, providing effective sealing performance for a closure and container package having carbonated contents can be demanding. Retention of carbonization for extended periods, and under varying temperature conditions, requires careful engineering of the closure 12 to provide the desired performance. At the same time, product quality assurance requires that the package provide reliable tamper-indication, with the closure 12 specifically configured to cooperate with the associated container to provide reliable tamper-evidence.

Notwithstanding these demands, a closure must be convenient for consumers to use, without requiring excessive application of torque during closure manipulation to effect removal from the associated container. The closure must lend itself to high-speed application to the container with automated capping equipment, with very low rates of misapplication.

In this content, it is highly desirable to minimize the quantity of polymeric material from which a closure is formed. The polymeric material represents a significant portion of the cost of the closure, and thus any material savings will eventually be achieved on a relatively large scale, given the extensive use of this type of packaging for carbonated products, such as carbonated beverages.

As will be further described, closure 12 has been specifically configured to provide the necessary performance characteristics, including sealing performance, while at the same time desirably minimizing the use of polymeric material from which the closure is formed, and the cost associated therewith. The closure is specifically configured for reliable tamper-indication attendant to partial or complete removal from the associated container, thus providing the desired quality assurance for consumers.

With further reference to the drawings, in the illustrated embodiment closure 12 comprises a unitary, one-piece closure cap 12 having a top wall portion 20, and an annular skirt portion 22 depending from the top wall portion. The skirt portion 22 is provided with internal thread formation 24 in the form of a plurality of thread segments which collectively define the internal thread formation. Notably, the internal thread formation 24 is preferably configured to provide a variable retention force, that is, provide a retention force which decreases in a direction away from the top wall portion 20. To this end, the thread formation can be configured in accordance with U.S. Patent Publication No. 2012/0091138, published Apr. 19, 2012, the disclosure of which is hereby incorporated by reference. In the illustrated embodiment, this variation in retention force is achieved by providing portions of the internal thread formation 24 which are further from the top wall portion 20 with a reduced thread profile, as illustrated. This preferred configuration of the internal thread formation 24 has desirably been found to improve the strip torque performance of the closure.

Closure 12 is configured for cooperative, sealing engagement with an associated container 14 of the closure and container package 10. In the illustrated embodiment, the container 14 is shown as having a so-called “CSD finish”, that is, a configuration in accordance with industry standards for carbonated soft drinks (this is sometimes designated as an “1881 finish”).

The closure 12 is configured for rotatable, threaded application to and removal from, container 14 by inter-engagement of internal thread formation 24 with external thread formation 16. Convenient manipulation of the closure 12 by consumers is facilitated by the provision of a plurality of axially extending external gripping knurls 26 on the exterior surface of the skirt portion 22.

As noted, in the illustrated embodiment of closure 12, the closure is of a unitary construction, and does not include a separate sealing liner element. While a closure configured in accordance with the present invention can include such a separate sealing liner, in the illustrated embodiment, the closure cap is provided with integral sealing features for providing the desired sealing cooperation with the associated container 14. Specifically, the closure 12 includes an inner plug seal element 30 which depends integrally from top wall portion 20. The inner plug seal element 30 is generally cylindrical, and defines an outwardly facing sealing surface for sealing engagement with a generally inwardly facing, inside surface of the associated container 14.

The sealing performance of the closure 12 is achieved by the further provision of an outer seal element 32 depending from top wall portion 20 inwardly of annular skirt portion 22. The outer seal element 32, which in the illustrated embodiment has an axial dimension less than the axial dimension of inner plug seal element 30, defines a generally inwardly facing sealing surface for engagement with the generally outwardly facing surface of the associated container 14.

In a presently preferred embodiment, enhanced sealing performance for the closure 12 is achieved by the provision of a plurality of circumferentially spaced, seal reinforcement elements 34 on the inside surface of skirt portion 22 radially outwardly of outer seal element 32. The reinforcement elements 34 are positioned adjacent the top wall portion 22, with the individual reinforcement elements being circumferentially spaced about the interior of the closure 12. The reinforcement elements can be configured in accordance with U.S. Patent Publication No. 2013/0175285, and are configured so that the reinforcement elements are engageable by the outer seal element 32 to limit outward deflection of the outer seal element, thus enhancing sealing cooperation of the outer seal element with the associated container 14. Impact resistance is also desirably enhanced.

As noted, tamper-evidence is an important capability for this type of closure, and to this end, closure 12 includes a tamper-evident band 40 which is at least partially detachably connected to the annular skirt portion 22. In the presently preferred form, a tamper-evident band 40 includes annular band portion 42 depending from skirt portion 22 to which the band portion is detachably connected. The tamper-evident band further includes an annular inner flange portion 44 extending inwardly from the lower margin of the annular band portion 42.

In a presently preferred embodiment, the inner flange portion 44 defines a plurality of circumferentially spaced openings or windows of 46 which are spaced from an inner free edge of the inner flange portion 44. The provision of these openings 46 desirably facilitates folding and inversion of the inner flange portion 44 while the orientation in which it is molded, shown in FIG. 3, to its in-use orientation, shown in FIG. 2. The provision of openings 46 has also been found to desirably enhance the tamper-resistance of the tamper-evident band construction, and facilitates inversion or reorientation of the Flange portion 44 from its molded orientation (FIG. 3) to its orientation (FIG. 2) when the closure is applied to a container.

As illustrated, the tamper-evident band 40 has a maximum outside dimension which is substantially aligned with a maximum outside dimension of skirt portion 22 at the external knurl pattern 26. This arrangement has been found to desirably spread the load during any side impact that can occur during transportation, or conveyance in the closure application line, over as much of the side length of the closure as possible. This desirably acts to reduce the stress on the frangible connection between the skirt portion and the tamper-evident band, which desirably limits unintended fracture of the closure, prior to closure removal by consumers.

The desired frangible connection between the tamper-evident band and skirt portion 22 is provided by a plurality of circumferentially spaced frangible bridges 48 (see FIG. 2) extending between the lower margin of skirt portion 22 and annular band portion of 42 of tamper-evident band 40. Each of the frangible bridges 48 is defined between circumferentially spaced scores 50 that extend into the closure between the skirt portion and the tamper-evident band. In the preferred practice of the present invention, the scores 50 are formed by the use of an interrupted scoring knife which has been found to desirably produce fewer stress concentrations on edges perpendicular to loads applied to the closure during application to the associated container, and during transportation and conveyance during closure application. Partially cut frangible bridges, as are sometimes employed, have been found to produce stress concentrations in direct line with typical loading to which closures are subjected. Therefore, the use of an interrupted knife scoring process results in the closure being able to absorb more load without the band breaking away from the skirt portion of the closure. This method of formation is preferred in the context of making the closure as light as possible, since the tamper-evident band has relatively less strength. With lower band strength, the frangible bridges need to be relatively weaker longitudinally so that the band still breaks properly during closure removal by consumers. The reduced stress concentrations and the direction of the load allow the bridges to be longitudinally weaker, while still being sufficiently strong in the lateral direction.

An aspect of achieving a lightweight closure in accordance with the present invention has been selection of polymeric material from which the closure is formed. In a presently preferred embodiment, closure 12 is formed from high-density polyethylene polymer having a density in the range of about 0.945 g/cm to about 0.97 g/cm. In a currently embodiment, a polymer designated Dow 1250 (DMDA-1250 or DMDC-1250), available from Dow Chemical, has a density of 0.955 g/cm, with a polymer formulated to include approximately 0.2 to 0.3% lubricant (such as erucamide) by weight. In a typical formulation, the polymer includes a colorant in the range of let-down ratios of 0.5 to 2.0 weight percent, in combination with a let-down ratio of nucleator masterbatch of 0.6-1.6 weight percent (actual nucleator parts per million: 300 to 800), which desirably reduces and minimizes dimensional variations in the closure, as can occur by the use of polymers having colorance.

The nucleator is a commercially available additive that seeds the material with sites for crystallization (such as calcium carbonate). Different colors nucleate differently, so the nucleator overpowers to the effect of the colorant and the material becomes crystallized very quickly, and therefore changes less once the closure is ejected from the tooling. The end result is that the closure comes out larger, with less dimensional variation both within and between colors. It has been found that this desirably leads to reduced variation in removal torque performance between different colors.

As noted, the illustrated embodiment of the closure 12 has been configured for an industry standard container finish. In a current embodiment of the present closure, the closure is configured as a 28 mm closure for a carbonated soft drink bottle finish, sometimes referred to as a 1881 finish. In the illustrated embodiment the closure 12 includes a top wall portion 20 having a nominal thickness of 0.040 inches, and a nominal skirt portion thickness at the root of the thread formation, of 0.035 inches. In this embodiment, the height of the closure from the top wall portion 22 to scores 50 has a nominal dimension of 0.466 inches, with the tamper-evident band 40 having a nominal dimension of 0.134 inches. Notably, a closure configured in accordance with these dimensions, as described herein above, has a weight of no more than about 1.95 g. Notably, this compares very favorably to commercially available closures having weights which vary from 2.2 g to 2.45 g, with the present closure still meeting sealing and impact resistance performance criteria. In this regard, the closure preferably exhibits an Aggregated Lightweight Performance Index of at least about 40, a Sealing Index greater than about 1.3, and a Strip Torque Index greater than about 15, as discussed below.

Performance for the present closure and container package, including Carbonated Soft Drink sealing performance, can be evaluated in accordance with the test protocols set forth in US Patent Publication No. 2011/0024423, published Feb. 3, 2011, the disclosure of which is hereby incorporated by reference.

As discussed above, an aspect of the present invention, including the lightweight closure of the package, is achieving the desired performance characteristics, including carbonation retention, while minimizing the quantity of the polymeric material from which the closure is formed. To this end, it is contemplated that a closure and container package embodying the present invention exhibit an Aggregate Lightweight Performance Index (ALPI) of at least about 40.

The ALPI is calculated from specific performance indices, including Sealing Index (SI) and Strip Torque Index (STI). For purposes of calculating the ALPI, the Sealing Index is weighted by a factor of twenty (20), and combined with the Strip Torque Index (this reflects the relative importance of the Sealing Index.)

The Sealing Index for a closure can be determined, in accordance with industry protocols, and the performance testing set forth in US Patent Publication No. 2011/00224423, wherein the Sealing Index equals the sum of (Average Retained CO2 volume/Initial Fill Volume)/total closure mass, at initial carbonation filling of 4.2, 4.5, and 4.7 volumes, after conditioning at 100 degrees F. for 2 weeks. A volume of carbonation is the amount of CO2 that water will absorb at atmospheric pressure and 60 degrees F.

The Strip Torque Index equals the average strip torque/total closure mass, at conditioning of 100 degrees F. for 24 hours.

The following comparative data set forth in Table 1 shows the combination of performance criteria provided by the present closure to exhibit an ALPI of at least about 40. In a current embodiment of the invention, referenced in the comparative data as OmniMiniXP, the measured Sealing Index and Strip Torque Index were used to calculate an ALPI of at least about 40, specifically 42.24. It will be noted that this level of performance, factoring in closure weight, was significantly beyond levels of performance determined for the comparative, commercially available closures.

TABLE 1 Sealing Index Initial Fill Volume 4.2 4.5 4.7 SI Mass Closure Average Retained CO2: 2 Weeks 100 F. Value 1.9 OmniMiniXP 3.54 3.74 3.87 1.31 2.451 UCL Flex Grip 3.58 3.73 3.88 1.02 2.2 UCL Sylon 3.58 3.7 3.87 1.14 2.43 Bericap 3.59 3.75 3.88 1.03 Strip Torque Index Initial Fill Volume Average STI Mass Closure Strip Torque Value 1.9 OmniMiniXP 30.3 15.95 2.451 UCL Flex Grip 31.2 12.73 2.2 UCL Sylon 25.8 11.73 2.43 Bericap 24.4 10.04 ALPI Initial Fill Volume Mass Closure 1.9 OmniMiniXP 42.24 2.451 UCL Flex Grip 33.18 2.2 UCL Sylon 34.44 2.43 Bericap 30.73

In connection with these performance criteria, configuring the closure to include a single lead thread formation is presently preferred, for use on a 28 mm closure finish (but not necessarily an 1881 finish.) Use of polymer of the specified density range (from about 0.9 grams/cubic centimeter to about 0.97 grams/cubic centimeter, and preferably from about 0.945 grams/cubic centimeter to about 0.97 grams/cubic centimeter) generally excludes higher cost polymers that may exhibit a higher density/higher modulus. The performance criteria contemplate use of a bottle or container of a specified material, wall thickness and potential volume that represents typical bottle presently found in the field.

Test Protocols Strip Torque Purpose

Determine the stripping resistance of a closure on a finish when turned in the wrong direction.

Test Equipment

-   SecurePak Model 50 MRA or TMS5000 Spring Torque Tester or equivalent     (computer interface model is also available) -   Environmental chamber capable of heating the test samples to     38±1° C. (100±2° F.) -   Hand chuck sized to closure that covers approximately 50% of the     closure height, or equivalent

Procedure

-   1. Randomly select 12 performs or filled and capped 12 bottles -   2. Condition the samples according to the chart below:     -   Closure Type Conditioning     -   Temperature     -   Conditioning Time     -   Aluminum ROPP No conditioning Necessary     -   All others 38±1° C. (100±2° F.) 24 hrs     -   If samples have been hot-filled, conditioning is not needed,         move on to the next step when samples cool to 38±1° C. (100±2°         F.). -   3. Place the sample in the torquemeter. If the sample was     conditioned or hotfilled, do not allow it to cool below 38±1° C.     before testing. -   4. Using the hand chuck, rotate the closure slowly in a clockwise     direction at a steady rate of 2.3 kg-cm (2 in-lbs.) per second until     the closure can be felt to “jump” the finish threads. -   5. Record the strip torque value. -   6. Repeat the procedure on the remaining samples.

TM-2.13: Drop Test: Closures Purpose

To ensure the plastic closure will not release if the bottle is accidentally dropped.

Process Flowchart

Plastic CSD Pressurized Non-Pressurized & Hot-Fill

-   -   1. Apply plastic closures to PET bottles containing carbonated         water at 4.2±0.1 CO2 gas volumes     -   2. Condition the bottles for a minimum of 16 hours at 4°         C.±1° C. (39±2° F.)     -   3. Drop first set of bottles from a height of 1.8 meters (72″)         vertically onto the base, and drop a second set of bottles         horizontally from 1.8 meters (72″)     -   4. Observe any failures of closure release and leakage

Principles of Operation

During the normal course of handling, there exists a potential for the package (bottle and closure together) to be dropped. It is essential that the closure remain on the bottle during and following any such impacts. This test simulates the drop impact which may occur.

Equipment

-   Equipment or chemicals to carbonate to 4.20±0.10 CO2 gas volumes -   Equipment to pressurize to 25 psi maximum using nitrogen     -   Closure application equipment (i.e., Alcoa single head capper or         equivalent; Vibrac Torque Tester in application mode, etc.) -   Temperature controlled chamber set for 4° C. (39° F.)+/−1° C. (2°     F.)     -   Drop leaf impact tester with impacting surface of 2′×2′ (minimum         area) 0.5″ flat steel plate in intimate contact with concrete         floor -   Plastic safety shields around impacting surface     -   Plastic bottle with appropriate finish (use largest commonly         sold size, i.e., 1 L or 2 L for plastic CSD closures, and i.e.,         20 fl. oz./600 ml for NCB Pressurized and Non-Pressurized         plastic closures)     -   Hot filling equipment with temperature capability of 83°+/−1° C.         (180° to 183° F.) (Mokon Model #310242, or equivalent) -   Safety glasses -   Thermally protective gloves, or equivalent

Reagents/Chemicals

Not applicable

Calibration

Not applicable

Testing Frequency

24 sample bottles

Test Procedures

-   -   1) Fill sample PET bottles to nominal contents:

a) Plastic CSD:

Fill with carbonated water at a CO2 level of 4.20+/−0.10 gas volumes and cap immediately.

-   -   2) Place samples in the 4° C. (39° F.)+/−1° C. (2° F.) chamber         for a minimum of 16 hours.     -   3) a) Plastic CSD:

After the conditioning period, remove the samples, one at a time, and drop the bottles from a height of 1.8 meters (72″) (measured from the top of the swing leaf plate in ready to drop position) based on the following:—first set of samples dropped vertically onto the bottle base

-   -   4) Observe and note any failures (closures which do not remain         on the finish following the initial impact). Additionally,         observe for any closures which leak following the initial         impact. Damage Type and Location Key Code

1. No damage

2. Bottle spilt/cracked

3. Piece(s) released

4. Closure released

5. Cracked closure

Calculations

Not applicable

Record Keeping

Quantity of samples tested.

Report the number of samples, which failed (inclusive of mode of failure and storage conditions and drop orientation), for each temperature and mode of impact.

Record all data.

From the foregoing, it will be observed that numerous modifications and variations can be effected without departing from the true spirit and scope of the novel concept of the present invention. It is to be understood that no limitation with respect to the specific embodiment illustrated herein is intended or should be inferred. This disclosure is intent to cover, by the appended claims, all such modifications as fall within the scope of the claims. 

What is claimed is:
 1. A lightweight closure, comprising: a closure cap having a top wall portion, and an annular skirt portion depending from said top wall portion, said skirt portion including external knurl pattern, and an internal thread formation for threaded engagement with an external thread formation of an associated container; and a tamper-evident band at least partially detachably connected to said skirt portion, said tamper-evident band being detachably connected to said skirt portion by a plurality of circumferentially spaced frangible bridges, each of said bridges being defined between scores that extend into said closure between said skirt portion and said tamper-evident band, said closure being formed from high-density polyethylene polymer having a density of about 0.945 grams/cubic centimeter to about 0.97 grams/cubic centimeter, and having an Aggregate Lightweight Performance Index of at least about
 40. 2. A lightweight closure in accordance with claim 1, including: an outer seal element depending from said top wall portion inwardly of said annular skirt potion, said outer seal element being generally annular, and defining a generally inwardly facing sealing surface for engagement with a generally outwardly facing sealing surface of said container.
 3. A lightweight closure in accordance with claim 2, including: a plurality of circumferentially spaced, seal reinforcement elements on the inside surface of said skirt portion radially outwardly of said outer seal element and adjacent said top wall portion, said reinforcement elements being engageable by said outer seal element to limit outward deflection of said outer seal element, to enhance sealing cooperation of said outer seal element with the associated container.
 4. A lightweight closure for a container in accordance with claim 1, including: an inner plug seal element depending from said top wall portion, said plug seal element being generally cylindrical, and defining an outwardly facing sealing surface for sealing engagement with a generally inwardly facing, inside surface of an associated container.
 5. A lightweight closure for a container in accordance with claim 1, wherein: said polymer includes a colorant, and a nucleator.
 6. A lightweight closure for a container in accordance with claim 1, wherein: said closure weighs no more than approximately 1.95 grams.
 7. A lightweight closure for a container in accordance with claim 1, wherein: said polymer includes approximately 0.2 to 0.3% lubricant by weight.
 8. A lightweight closure for a container in accordance with claim 1, wherein: said tamper-evident band includes an annular band portion depending from said skirt portion that is detachably connected thereto, and an annular inner flange portion, extending inwardly from a lower margin of said annular band portion, said inner flange portion defining a plurality of circumferentially spaced openings spaced from a free edge thereof.
 9. A lightweight closure for a container in accordance with claim 1, wherein said internal thread formation is configured to provide a variation in retention force which decreases in a direction away from said top wall portion.
 10. A lightweight closure, comprising: a closure cap having a top wall portion, and an annular skirt portion depending from said top wall portion, said skirt portion including external knurl pattern, and an internal thread formation for threaded engagement with an external thread formation of an associated container; and a tamper-evident band at least partially detachably connected to said skirt portion, said tamper-evident band being detachably connected to said skirt portion by a plurality of circumferentially spaced frangible bridges, each of said bridges being defined between scores that extend into said closure between said skirt portion and said tamper-evident band, said closure being formed from high-density polyethylene polymer having a density of about 0.945 grams/cubic centimeter to about 0.97 grams/cubic centimeter, and having a Sealing Index greater than about 1.3.
 11. A lightweight closure, comprising: a closure cap having a top wall portion, and an annular skirt portion depending from said top wall portion, said skirt portion including external knurl pattern, and an internal thread formation for threaded engagement with an external thread formation of an associated container; and a tamper-evident band at least partially detachably connected to said skirt portion, said tamper-evident band being detachably connected to said skirt portion by a plurality of circumferentially spaced frangible bridges, each of said bridges being defined between scores that extend into said closure between said skirt portion and said tamper-evident band, said closure being formed from high-density polyethylene polymer having a density of about 0.945 grams/cubic centimeter to about 0.97 grams/cubic centimeter, and having a Strip Torque Value of greater than about
 15. 12. A lightweight closure, comprising: a closure cap having a top wall portion, and an annular skirt portion depending from said top wall portion, said skirt portion including external knurl pattern, and an internal thread formation for threaded engagement with an external thread formation of an associated container, said internal thread formation being configured to provide a variation in retention force which decreases in a direction away from said top wall portion; an outer seal element depending from said top wall portion inwardly of said annular skirt potion, said outer seal element being generally annular, and defining a generally inwardly facing sealing surface for engagement with a generally outwardly facing sealing surface of said container, and a tamper-evident band at least partially detachably connected to said skirt portion, said tamper-evident band being detachably connected to said skirt portion by a plurality of circumferentially spaced frangible bridges, each of said bridges being defined between circumferentially spaced scores that extend into said closure between said skirt portion and said tamper-evident band, said closure being formed from high-density polyethylene polymer having a density of about 0.945 grams/cubic centimeter to about 0.97 grams/cubic centimeter, said polymer including a colorant, and a nucleator to minimize dimensional variations of the closure.
 13. A lightweight closure in accordance with claim 12, including a plurality of circumferentially spaced, seal reinforcement elements on the inside surface of said skirt portion radially outwardly of said outer seal element and adjacent said top wall portion, said reinforcement elements being engageable by said outer seal element to limit outward deflection of said outer seal element, to enhance sealing cooperation of said outer seal element with the associated container, and
 14. A lightweight closure in accordance with claim 12, including an outer seal element depending from said top wall portion inwardly of said annular skirt portion, said outer seal element being generally annular, and defining a generally inwardly facing sealing surface for engagement with a generally outwardly facing sealing surface of said container, and an inner plug seal element depending from said top wall portion, said plug seal element being generally cylindrical, and defining an outwardly facing sealing surface for sealing engagement with a generally inwardly facing, inside surface of an associated container.
 15. A lightweight closure in accordance with claim 12, wherein said tamper-evident band includes an annular band portion depending from said skirt portion that is detachably connected thereto, and an annular inner flange portion, extending inwardly from a lower margin of said annular band portion, said inner flange portion defining a plurality of circumferentially spaced openings spaced from a free edge thereof.
 16. A lightweight closure in accordance with claim 12, including an inner plug seal element depending from said top wall portion, said plug seal element being generally cylindrical, and defining an outwardly facing sealing surface for sealing engagement with a generally inwardly facing, inside surface of an associated container.
 17. A package, comprising: a container having carbonated contents; and a lightweight closure, comprising a closure cap formed from a polymer and having a top wall portion, and an annular skirt portion depending from said top wall portion, said skirt portion including external knurl pattern, and an internal thread formation for threaded engagement with an external thread formation of an associated container; and a tamper-evident band at least partially detachably connected to said skirt portion, said tamper-evident band being detachably connected to said skirt portion by a plurality of circumferentially spaced frangible bridges, each of said bridges being defined between scores that extend into said closure between said skirt portion and said tamper-evident band, an outer seal element depending from said top wall portion inwardly of said annular skirt potion, said outer seal element being generally annular, and defining a generally inwardly facing sealing surface for engagement with a generally outwardly facing sealing surface of said container, and an inner plug seal element depending from said top wall portion, said plug seal element being generally cylindrical, and defining an outwardly facing sealing surface for sealing engagement with a generally inwardly facing, inside surface of an associated container, wherein said closure has a weight of no more than about 1.95 grams, and an Aggregate Lightweight Performance Index of at least about
 40. 18. A package in accordance with claim 17, wherein said polymer includes approximately 0.2 to 0.3% lubricant by weight, a colorant, and a nucleator to minimize dimensional variations of the closure.
 19. A package in accordance with claim 17, wherein said closure being is formed from high-density polyethylene polymer having a density of about 0.945 grams/cubic centimeter to about 0.97 grams/cubic centimeter, said polymer including a colorant, and a nucleator to minimize dimensional variations of the closure.
 20. A package in accordance with claim 17, including a plurality of circumferentially spaced, seal reinforcement elements on the inside surface of said skirt portion radially outwardly of said outer seal element and adjacent said top wall portion, said reinforcement elements being engageable by said outer seal element to limit outward deflection of said outer seal element, to enhance sealing cooperation of said outer seal element with said container. 